Antitank weapons such as DRAGON, VIPER and the 90 mm Recoilless Rifle achieve their primary velocity in the launch tube. In the case of DRAGON other propulsive means are used to sustain rocket velocity. This means that the propellant must be expended in a short time so that the combustion pressures are not excessive when the rocket or projectile exists the muzzle of the launcher. At present, recoilless rifle design demands relatively large throat area in order that sufficient propellant gases are discharged to the rear to counter balance the opposing (forward) projectile momentum. Some of these recoilless designs use a combined nozzle closure/shot start device. But in these devices, when the nozzle closure is released the effect of full nozzle opening is immediate and gas flow is controlled by the full nozzle throat. This of course places considerable stresses on the propellant being used to drive the projectile. In order to get high projectile velocity with reasonably short launch tubes, high operating pressure is required. High operating pressure in turn requires large propellant burning surface area. When the requirements for large throat and burning surface areas are coupled, very thin propellant webs result. Thin web propellant is subject to breakage, especially at cold temperatures. To overcome this problem, fiber reinforced propellant has been explored but showed little improvement. In addition, high pressure drives the motor case weight up and reduces efficiency of the rocket. Therefore, there is a need for a device which can accelerate a rocket or projectile to high velocity, while maintaining the recoilless feature of the launcher, and overcome the attendant propellant break-up problem.
Accordingly, it is an object of this invention to provide a high efficiency propulsion system which overcomes difficulties associated with other devices of this type and still accelerate a rocket or projectile to the required high velocity, thus demonstrating the high propulsion efficiency through delivered specific impulse (muzzle velocity.times.rocket or projectile muzzle mass.div.propellant weight).
Another object of this invention is to provide a high efficiency propulsion system that can be used as a training device at low cost.
Still another object of this invention is to provide a high efficiency propulsion system in which the flow path for the gases produced from the buring propellant is such that any broken propellant will tend to be trapped and caused to burn before reaching the throat section of the combustion chamber.
Yet another object of this invention is to provide a high efficiency propulsion system in which the launch tube can be used many times by replacing only the rocket or projectile and gas generator with its appropriate ingniter means which causes launching of the projectile.
Other objects and advantages of this invention will be obvious to those skilled in this art.